A B C D E F G H I J K L M N O P Q R S T U V W X Y Z Appendix

Ohmdenosaurus

Taxon: Sauropoda

Name means: “Ohmden lizard,” after the town of Ohmden in Germany

Pronounced: ohm-DEN-uh-SAW-rus

Length: about 10 – 13.5 ft (3 – 4 m)

Time: Early Jurassic, 191 mya

Place: Germany

This early plant-eating sauropod was once mistaken for a water-bound plesiosaur when a lower leg bone was incorrectly identified as the arm of the aquatic reptile. Named in 1978, Ohmendosaurus is tentatively considered a vulcanodontid --- an intermediate group between prosauropods and sauropods.

Oligosaurus

Name means: “small lizard”

Pronounced: oh-LIG-uh-SAW-rus

This dinosaur is considered to be RHABDODON.

Omeisaurus

Taxon: Sauropoda

Name means: “Mount Emei lizard”

Pronounced: UH-may-SAWR-us or OH-may-SAWR-us

Length: about 33 – 50 ft (10 – 20 m)

Time: Late Jurassic, 156 – 145 mya

Place: China

Date: 1939

This medium-sized sauropod had an unusually long neck, even for that group of giants. Omeisaurus was named in 1939 for a sacred Chinese mountain.

Omosaurus

Taxon: Sauropoda

Name means: “forelimb lizard” or “Mount Emei lizard”

Pronounced: OH-muh-SAW-rus

Length: 54 – 68 ft (16.5 – 28 m)

time: Late Jurassic

place: China

Many individuals of this sauropod species were discovered within a 3000-square-meter area. This close grouping suggests that Omosaurus, named in 1939, may have been a sociable dinosaur species, traveling, feeding or nesting in herds. When paleontologists have finished studying this copious material, this will be one of the best-known sauropod dinosaurs. It may also prove, as most researchers believe, that Omosaurus is actually part of the genus Dacentrus.

Ornatotholus

Taxon: Pachycephalosauria

Name means: “decorated dome”

Pronounced: or-NAT-uh-THOH-lus

Length: 6.6 ft (2.5 m)

Time: Late Cretaceous, 75 mya

Place: Alberta

Dinosaur experts first described this bone-headed pachycephalosaur as a possible female Stegoceras. Further analysis showed that the remains belonged to a new species of the rare thick-skulled pachycephalosaurs, and Ornatotholus was named in 1983. Ornatotholus had a low skull-dome with bony knobs and a grove running across it.

Onychosaurus

Name means: “barbed lizard”

Pronounced: ON-ik-o-SAWR-us

This dinosaur is considered to be RHABDODON.

Opisthocoelicaudia

Taxon: Sauropoda

Name means: “hollow-backed tail vertebrae”

Pronounced: oh-PIS-thuh-SEE-li-KAW-dee-uh

Length: 40 ft (12 m)

Time: Late Cretaceous, c. 75 – 70 mya

Place: Mongolia

Generally considered to be a camarasaur, the long-necked sauropod Opisthocoelicaudia may instead have been an advanced titanosaur. It has been suggested that the skeletal remains of this dinosaur might be the body of the incompletely-known Nemegtosaurus. Opisthocoelicaudia was named in 1977.

Oplosaurus

Name means: “armored lizard”

Pronounced: OP-lo-SAWR-us

This dinosaur was probably the same animal as PELOROSAURUS.

Orinosaurus

Name means: “mountain lizard”

Pronounced: o-RIEN-o-SAWR-us

This dinosaur is considered to be EUSKELOSAURUS.

Ornithodesmus

Taxon: probably Theropoda

Pronounced: or-NITH-oh-DES-mus

Length: Small

Time: Late Cretaceous

Once considered a primitive bird, then a pterosaur, then a troodontid or possible Deinonychus relative, this small meat-eating dinosaur continues to defy easy classification.

Ornithoides

Name means: “bird form”

Pronounced: OR-nih-THOY-deez

This dinosaur is now known as SAURORNITHOIDES.

Ornitholestes

Taxon: Theropoda Coeluridae

Name means: “bird robber”

Pronounced: or-NITH-o-LES-teez

Length: 3.5 – 7 ft (1 – 2 m)

Time: Late Jurassic, 156 – 145 mya

Place: Wyoming, Utah

A light, agile predator with a crest above its nose, the nimble Ornitholestes was named in 1903.

Ornithomerus

Name means: “bird femur”

Pronounced: OR-nith-oh-MEER-us

This dinosaur is now considered to be RHABDODON.

Ornithomimus

Taxon: Theropoda Ornithomimosauria

Name means: “bird mimic”

Pronounced: OR-ni-thuh-MYE-mus

Length: 12 ft (3.5 m)

Time: Late Cretaceous, 76 – 65 mya

Place: Colorado, Utah, Montana, Wyoming, Alberta

Date: 1890

The discovery of Ornithomimus helped Marsh to establish the long-legged ornithomimid “ostrich-mimic” group as a whole. Like Struthimimus, this dinosaur had a small head, a toothless mouth, a long neck and long arms with nimble fingers. Its hind legs and rod-like tail were superbly adapted for speed and agility. While they were once considered to have been herbivorous dinosaurs, some scientists now believe that ornithomimids may have lived on a diet of insects, eggs, or small, soft-bodied reptiles and mammals. Marsh named the amazing Ornithomimus in 1890.

Ornithopsis

Pronounced: OR-ni-THOP-sis

This dinosaur is generally believed to be the same as PELOROSAURUS.

Ornithotarsus Doubtful name. Possibly Hadrosaurus.

Taxon: Hadrosauria

Name means: “bird tarsus”

Pronounced: (OR-ni-thuh-TAHR-sus)

Length: Moderate

time: Late Cretaceous

place: New Jersey

The bird-like fused leg bones of Ornithotarsus at first led researchers to believe that the poorly-preserved dinosaur had been a small member of the meat-eating theropods. Further study, however, showed that the fossilized bones actually belonged to a large duckbilled plant-eater. Ornithotarsus was named by Cope in 1869 and later revised by Marsh. Some scientists believe that this was a species of Hadrosaurus.

Orodromeus

Taxon: Ornithopoda Hypsilophodontidae

Name means: “mountain runner”

Pronounced: OR-uh-DROH-mee-us

Length: 8 ft (2.5 m)

Time: Late Cretaceous, 77 – 73 mya

Place: Montana

This small plant-eating hypsilophodontid had strong, lean hind legs and was probably a capable two-legged runner. Named in 1988, Orodromeus may have been menaced by the predatory Troodon, remains of which were found in the same place and from the same general time.

Orosaurus

Name means: “mountain lizard”

Pronounced: OR-uh-SAW-rus

Remains from this now-invalid genus have been assigned to ORINOSAURUS and EUSKELOSAURUS.

Orthogoniosaurus

Taxon: probably Carnosauria

name means: “straight-angled lizard”

pronunciation: OR-thuh-GOH-nee-uh-SAW-rus

Length: Unknown

time: Late Cretaceous

place: India

Named for a single, poorly-preserved tooth with both serrated and unserrated qualities, Orthogoniosaurus has proven difficult to classify without question. This may have been a meat-eating carnosaur, but it is presently impossible to say for certain.

Orthomerus

Taxon: Hadrosauria

name means: “straight femur”

pronunciation: or-THOM-uh-rus

Length: Small (juvenile)

time: Late Cretaceous

place: The Netherlands

Among the first species to be classified as a “duckbilled” hadrosaurid in Europe, Orthomerus was described in 1883 based on the fossilized remains of a juvenile. This sample is also regarded as the junior synonym for Telmatosaurs.

Oshanosaurus

pronunciation: oh-SHAN-uh-SAW-rus

time: Early Jurassic, 180 mya

place: China

This small dinosaur plant-eater may have been a heterodontosaurid or a primitive plant-eater with canine teeth. But being sure without much fossil study is impossible at this point.

Othnielia

Taxon: Ornithopoda Hypsilophodontidae

Name means: “for Othniel,” after paleontologist Othniel Marsh

Pronounced: oth-NEE-lee-uh

Length: 4.6 feet (1.4 m )

Time: Late Jurassic, 156 – 145 mya

Place: Colorado, Utah, Wyoming

Date: 1977

A member of the primitive, plant-eating hypsilophodontid dinosaurs, Othnielia closely resembled Hypsilophodon, but differed in its vertebrae and its more slender hindfoot and delicate toes. Othneilia was named in 1977 for pioneer paleontologist Othniel Charles Marsh.

Ouranosaurus

Taxon: Ornithopoda Iguanodontidae

Name means: “brave lizard”

Pronounced: oo-RAN-uh-SAW-rus

Length: 24 ft (7 m)

Time: Early Cretaceous, 115 mya

Place: Niger, Africa

This large plant-eating iguanodont had a long, slender snout with a short, horny beak. Unlike most of the spike-thumbed iguanodonts, Ouranosaurus had distinctive long spines projecting from the tops of its backbones, creating a high humped or sail-finned profile. This tall spinal ridge may have been brightly-colored or otherwise marked to attract mates or to compete with other members of the same species over territory. It may also have served to cool an overheating dinosaur by radiating heat into the air. Ouranosaurus was named in 1976.

Oviraptor

Taxon: Oviraptorosauria

Name means: “egg robber”

Pronounced: OH-vi-RAP-tor

Length: 5 – 8 ft (1.5 – 2.5 m)

Time: Late Cretaceous, about 88 – 70 mya

Place: Gobi Desert, Mongolia

Oviraptor was a long-armed, dexterous dinosaur which was long considered to have been an egg-eater. The recent discovery that the nest one Oviraptor had died while allegedly “robbing” contained the eggs of its own species, however, has cast great doubt upon the original accusation. Since then, additional Oviraptor finds have revealed that this dinosaur perched over its clutch of eggs for protection and warmth, a brooding behavior very much like that seen in birds today. This dinosaur’s odd, toothless skull bore a high crest, a short beak and a pair of conical prongs on the roof of the mouth. Although the diet of Oviraptor unknown and the subject of much conjecture, the strong beak and spikes might have aided in crushing anything from bone to eggshell to hard seeds to the shells of marine mollusks. Oviraptor was given its unfortunate name in 1924.

Ovoraptor

Name means: “egg robber”

Pronounced: OH-voh-RAP-tor

This is now known to be VELOCIRAPTOR.

Ozraptor

Taxon: Theropoda

Name means: “Australian plunderer”

Pronounced: oz-RAP-tor

Length: 6 – 10 ft (2 – 3 m)

Time: Middle Jurassic, 177 – 169 mya

Place: Australia

Named in 1998, this small meat-eating theropod was described based on single leg bone. The fossil was at first thought to have belonged to an ancient turtle. In 1998, Ozraptor became the first dinosaur from Western Australia to be scientifically named.